The keyboard folio was also better for the RMPP since I often experienced loose contact with the one on the BTUCP when I used it on my lap (flat surfaces were good once I set it up). Otoh, the material used in the BTUCP was much better since the RMPP one uses a polyster weave which often leaves me with slight goosebumps. Additionally, the keyboard folio isn't a feature I use often.
I really can't talk about the others so for all I know, Scribe or supernote might be a lot better. RMPP does have a 90 days no questions asked return policy if you want to try it out (though I'm not sure how much that's worth).
Thanks for mentioning these other devices. I used to have a Kindle Paperwhite (I see it is different than Scribe), butI lost it. I'll explore the other options.